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Summary: The evaporative cooling technique is an efficient approach for cooling application. This study aims to establish a performance evaluation method to advance the appropriate design for multistage indirect evaporative cooling systems. A mathematical formulation has been developed for the indirect evaporative cooler (IEC). After the validation, the mathematical model was used to analyze the evaluation criteria by considering the simultaneous influence of the cooling effectiveness, the pressure drop, and the cooling capacity of the multistage IEC operating in two modes. The Mode‐1 IEC is a conventional counterflow unit, while the Mode‐2 IEC employs a regenerative M‐cycle arrangement. The IECs are operated in a tandem arrangement. The multistage system is capable of improving the cooling performance and reducing the outlet air temperature. In addition, the multistage system displays a higher pressure drop resulting in a lager consumption of fan power. The analysis of performance evaluation criteria indicates that the appropriate maximum stage is suggested to be three‐stage and two‐stage for the Mode‐1 and the Mode‐2 IEC, respectively. [ABSTRACT FROM AUTHOR]

A liquid desiccant air dehumidification system driven by heat pump was established. The performance of cross-flow dehumidifier/regenerator was experimentally investigated. The empirical correlations of Sherwood number for dehumidification/regeneration were obtained by fitting the experimental data. On the basis of the empirical correlations of Sherwood number and thermodynamics analysis of heat and mass transfer process for dehumidifier/regenerator, a cross-flow heat and mass transfer model was established. The effects of air and solution parameters on the dehumidification/regeneration performance were analyzed. The number of mass transfer units and the height-to-length ratio of the packing module were also studied. The results show that there exist optimal number of mass transfer units and height-to-length ratio in the dehumidifier/regenerator. [ABSTRACT FROM AUTHOR]

Abstract A liquid desiccant-indirect evaporative cooling (LD-IEC) system has been proposed. The design is able to dehumidify and cool the product air simultaneously in one unit. A computational model has been developed to determine the performance of the heat and mass transfer process. The validation of the model demonstrated good agreement with the experimental data to within 10%. The detailed air treatment process has been theoretically studied. The thermal performance of the LD-IEC has been evaluated. Simulation results showed that the outlet temperature and humidity ratio were influenced by the liquid desiccant film length, intake air temperature, and intake air humidity ratio. For a specific inlet temperature and humidity ratio condition, a desired outlet condition can be obtained by adjusting the length of the liquid desiccant film. [ABSTRACT FROM AUTHOR]

Abstract A hybrid evaporative pre-cooled air-conditioning system is introduced for tropical climate applications. The indirect evaporative heat exchanger is employed to pre-cool the ambient humid air before passing through the vapor compression system. A computational model has been developed for the evaporative pre-cooling process. We validated the model by comparing the simulated outlet air temperature against experimental data. The validated model is then used to investigate the performance of the indirect evaporative heat exchanger in terms of the air temperature and humidity profiles. The pre-cooling process is able to reduce the product air temperature and condense water in the product channel. Consequently, the hybrid evaporative pre-cooled air-conditioning system is able to achieve a potential energy saving due the pre-cooling effect and the improvement of the chiller's efficiency. [ABSTRACT FROM AUTHOR]

The hollow fiber membrane-integrated evaporative cooler (MEC) is considered as a promising strategy for space air conditioning applications. For a counter-flow MEC, the appropriate fiber specification and flow configuration need to be identified to improve its comprehensive performance. A numerical model was developed to capture the coupled heat and mass transfer process, and its feasibility was verified by measured data. The influence of fiber specifications and flow configuration on its cooling, space-saving, energy and water conservation performance were investigated. The results revealed that a reasonable fiber specification required a packing fraction of about 0.1 and a length slightly longer than the air channel's entrance length, while the inner diameter and membrane thickness should be determined based on the priority index. The flow configuration of air flowing via shell-side and water going through tube-side was more suitable for counter-flow MEC, which was more energy efficient while maintaining cooling ability. In addition, the contribution of each component's resistance to the total heat and mass transfer resistance would fluctuate as the influencing factors changed. In general, the total heat transfer resistance was dominated by the air-side convective resistance, while the main contributor to the total mass transfer resistance was the membrane resistance. • The counter-flow hollow fiber membrane module is proposed for evaporative cooling. • A numerical model is developed and validated with experimental measurements. • The composition of the heat and mass transfer resistance is quantified. • Appropriate fiber specification and flow configuration are determined. [ABSTRACT FROM AUTHOR]